1. Field of the Invention
The present invention relates to an anti-inflammatory composition, a diagnostic method and a diagnostic kit for inflammatory disease prepared by using antibody specifically binding to CD93 or soluble fragment of the same.
2. Description of the Related Art
Human CD93 (C1qRp, AA4.1(mouse)) is type 1 transmembrane glycoprotein located on chromosome 20, p11.21 (Malhotra, R. et al., 1993. Immunology 78: 341-348; Nepomuceno, R. R. et al., 1997. Immunity 6: 119-129; Steinberger, P. et al., 2002. Biol. 71: 133-140). According to the previous reports, this protein is involved in cell-cell interaction during B cell development and phagocytosis (Petrenko, O. et al., 1999. Immunity 10: 691-700; Norsworthy, P. J. et al., 2004. J. Immunol. 172: 3406-3414; Nepomuceno, R. R. et al., 1997. Immunity 6: 119-129; McGreal, E. P. et al., 2002. J. Immunol. 168: 5222-5232).
CD93 is composed of 652 amino acids including leader sequence, c-type carbohydrate-sensing domain, 5 EGF-like domains, mucin domain, one transmembrane domain, and intracellular domain of 47 amino acids (Nepomuceno R. R. et al., 1997. Immunity 6:119-129; Park, M. et al., 2003. J. Cell Physiol. 196: 512-522; Nepomuceno, R. R. et al., J. Immunol. 162:3583). CD93 is expressed in myeloid lineages, hematopoietic stem cells, NK cells, platelets, microglia, and endothelial cells, etc (Nepomuceno, R. R. et al., 1997. Immunity 6:119; Nepomuceno, R. R. et al., 1998. J. Immunol. 160:1929; Danet G. H. et al., Proc Natl Acad Sci USA 2002; 99:10441-5; Lovik G. et al., J Immunol 2000; 30:3355-62; Fonseca M. I. et al., J Leukoc Biol 2001; 70:793-800; Webster, S. D. et al., 2000. J. Leukocyte Biol. 67:109). A previous report stated that CD93 was not expressed in tissue macrophages but expressed in vascular endothelial cells in a large scale (Petrenko, O. et al., 1999. Immunity 10:691; Dean, Y. D. et al., J. Immunol. 31:1370; Fonseca, M. I. et al., 2001. J. Leukocyte Biol. 70:793.). CD93 was presumed to be involved in C1q-mediated enhancement of phagocytosis, according to a research using anti-CD93 antibody, suggesting that CD93 might be acting as C1q receptor. However, consequent experiments proved that CD93 did not bind directly to C1q (Nepomuceno, R. R. et al. 1999. J. Immunol. 162:3583; McGreal, E. P. et al., 2002. J. Immunol. 168:5222; Steinberger, P. et al., 2002. J. Leukocyte Biol. 71:133).
In the experiment with CD93 knock-out mouse, a problem in eliminating killed cells was caused by the absence of CD93. However, in the in vitro experiment, no functional abnormality was observed (Guan, E. et al., 1994. J. Immunol. 152: 4005-4016; Norsworthy, P. J. et al., 2004. J. Immunol. 172: 3406-3414; Norsworthy, P. J. et al., 2004. J. Immunol. 172: 3406-3414). Phagocytosis plays an important role in the early stage of immune response, that is the function is very important in eliminating killed cells (Brown, E. J. (1995) Phagocytosis. Bioessays 17, 109-117).
Recent studies provided some clues to answer the questions about such functions. For example, it has been reported that shedding of CD93 occurs in the pro-inflammatory state of TNF-α and LPS, etc., so that ectodomain of CD93 is cut off (Park, M. et al., 2003. J. Cell Physiol. 196: 512-522.; Suzanne S. Bohlson et al., 2005. J. immunol. 175: 1239-1247). It has also been reported that CD93 is fragmentized into soluble fragments in U937 cells by the treatment of PMA (phorbol-12-myristate-13-acetate) (Ikewaki N., Tamauchi H., and Inoko H. 2007. Decrease in CD93 expression in a human monocyte-like cell line (U937) treated with various apoptosis-inducing chemical substances. Microbiol. Immunol., 51(12):1189-1200). Besides, WO 2008/082519 states that CD93-related polymorphs are very useful for the diagnosis of type-1 diabetes and Lupus Erythematosus. However, there have no reports made yet about the use of CD93 for the treatment or diagnosis of inflammatory disease.
Thus, the present inventors studied the possibility of the involvement of CD93 or its soluble fragment in inflammation. As a result, the present inventors confirmed that a soluble fragment of CD93 has excellent anti-inflammatory effect and CD93 or its soluble fragment is over-expressed in the presence of inflammation inducing substances or inflammatory environment, so that the inventors further completed this invention by proving that a soluble fragment of CD3 can be used as an active ingredient of an anti-inflammatory composition and CD93 or a soluble fragment thereof can also be used as a diagnostic marker for inflammatory disease.